Process for the production of metal powder or dust



May 27, 1924., Y 1,495,961

v M. H. NEWELL. ETAL PROCESS FOR THE PRODUCTION OF. METAL rowDER R DUSYT Filed Feb. 15, 1923 paw s-sheen! INVENTORS v Minion M/Ve wel Z =-EvaZc1 fnderson A TTORNE Y May 27, 1924. 1,495,961

' M. H. NEWELL. ET AL.

PROCESS FOR THE PRODUCTION OF METAL POWDER OR DUST Filed Feb. 5, 1923 2 Shams-shew 2 Figure 3.

INVENTORS: Mr'mon fl- Ne we I I A TTORNE Y Patented Ma 27 1924.

UNITED STATES PATENT 1,495,961 OFFICE.

MIN'I'ON H. NEWELL, OF PALO ALTO, AND EVALD ANDERSON, OF ALHAMBRA, CALI- FORNIA, ASSIGNORS TO INTERNATIONAL PRECIPITATION COMPANY, .ANGELES, CALIFORNIA, A CORPORATION OF CALIFORNIA.

I PROCESS FOR,THE PRODUCTION OF POWDER OR DUST.

Application filed February To all whom it may concern:

Be it known that we, MINToN H. NEWELL and EVALD ANDnnsoN, citizens of the United 7 States, residing, respectively, at Palo Alto, in the county of Santa Clara, and at Alhambra, in the county of Los Angeles, State of California, have invented a new and useful Process for the Production of Metal Powder or Dust, of which the following is a specification. v

This invention relates more especially to the production of finely divided zinc, "Zinc powder or dust, which is e'specially'adapted for use as a precipitant in the recovery of gold, silver and other 'metals by the cyanide process and as a reducing agent in the. dye industry, and for other purposes. The process may, however, be used for production of dust or powder of other metals.

The main object of the present invention is to provide for production of said zinc powder in a state of extremely fine division and having a high precipitating or reducing efiiciency. Our invention consists essenti'ally in producing zinc vapor by volatilization of metallic zinc or otherwise, bringing such zinc vapor, while still at high temperature into contact with a relatively cooler gaseous medium containing an oxidizing l0 constituent, thereby causing condensation of the zinc in finely divided form and then separating the finely divided zinc so condensed from the gases. Our process also comprises circulation of the gases in such 86 manner that the same gas is used rapidly in cyclic operation for cooling further quanti-- ties of zinc vapor to condense the same to finely divided zinc, definite and regulated quantity of oxidizing agent being supplied to the gases to maintain the required oxidizing property thereof. The accompanying drawings illustrate apparatus suitable for -our invention and referring thereto Fig. 1 is a plan and Fig. 2 is a side elevation section of a preferred form of such apparatus, the retorting furnace being shown in section. Fig. 3 is a vertical section of a modified form thereof.

' Referring to Fig. 2, we; have indicated 1 at 1 a zinc volatilizing retort provided with a suitable furnace means 2 for heating the same and with anoutlet 3 discharging into a casing orchamber 4 which serves as a condensing and settling chamber, said chamber 15, 1923. Serial 1%. 619,324.

beingprovided at its lower portion with a suitable means such as a funnel or hopper 5, for receiving the zinc powder and with a gate or discharge means 6, whereby the settled powder maybe withdrawn from time to time in a suitablereceiving'means. .Said chamber 4 is sealed by clay 14, or other suitable material so as to make an airtight joint between chamber 4 and furnace 2. Means are provided for circulating the gas from the cooler part of the chamber 4 to the portion thereof adjacent to the mouth or outlet of the retort 1. For this purpose a fan or blower 7 by suitable means and having its intake 8 connected to a portion of the chamber4 removed from retort 1 and its outlet connected by a conduit 9 which discharges into the chamber 4 adjacent to said outlet 3 of the retort 1, or in position to direct current of gas therefrom into contact with the vapor issuing from said outlet.

Means are alsoprovided for a supply of definite and regulated amount of oxidizing agent to the chamber 4; For this purpose a so-called breathingbag indicated at 10 may be provided, communicating to an opening 11 with the chamber 4 and exposed to the outer air, said bag being of suitable may be provided, operated permeable material such as cloth, so as to permit restricted. communication of gases therethrough, the amount of restriction depending on the closeness of weave of the cloth 'so' that any desired amount ofrestriction can be secured by properly choosing a cloth of suitable texture. The wall of chamher 4 may be provided with an opening normally closed by plug 13 to serve as a siglrt opening and for the passage of a tool for Y clean ing theinterior of the casing.

Our process may be carried out in the above, described apparatus as follows: Spelter, zinc dross or other material containing metallic zinc or zinc alloy,.is introduced into the retort 1 and the latter is then heated so as to volatilize the zinc, the zinc vapor'escaping through the outlet-3 into the chamber 4. Immediately on entering Tsaid chamber 4, the zinc vapor, While stlll at a high temperature is brought into contact with relatively gas discharged from the conduitv9, thereliychilling the zinc vapor and causing it to condense in-the form of dust.

or powder. Assuming that the operation is started with atmospheric air contained in the chamber 4, the effect of the oxidizing action of the air on the zinc vapor'will be in the first instance to produce oxideof zinc,

but in continued operation of the process sufficiently large superficial area to provide for the required cooling of the 'gases contained therein so that the gas drawn from the chamber at a point remote from the retort and then forced by the blower to a part adjacent to the retort, is sufliciently cool to produce the required condensing action on the zinc vapor. Sufiicient air is continually or intermittently supplied through the means 10 to maintain the proportion of oxygen in the gas in the chamber 4, required for most effective production of the finely divided zinc powder. We have found that for some purposes it'is desirable to maintain an oxygen content such that the resulting zinc dust contains not less than 84 per cent or more than 96 per cent metallic zinc.

In further explanation of the operation of the so-called breathing bag 10, it may be stated that in the operation of the apparatus slight fluctuation of pressure results in chamber 4, probably due to intermittent supersaturation of the gases with zinc vapor, followed by or alternating with periods of rapid condensation which are accompanied Y by corresponding degrees of pressure within the chamber and during such periods of decreased pressure a certain amount of atmospheric. air will pass into the chamber, thereby introducing a fresh supply of oxygen. On the other hand, during periods when the supersaturated condition is building up in the chamber, there is a corresponding increase of pressure during which a certain amount of gases will be expelled through the bag 10, said bag, however, preventing the outward passage of suspended zinc'powder with such expelled gases. y We have found that both the chilling of the vapor produced by circulation of the gases as stated and the presenceof a limited amount of oxidizing agent are necessary for the production of the most effective zinc dust for certain purposes; for example, as a precipitant in the cyanide process of extraction of metals. In place of air, any oxidizing agents may be used, by which controlled partial oxidation of zinc vapor or zinc dust can be carried on, for example, carbon dioxide, steam or other gas or vapor containing oxygen in combined form, but capable of producing an oxidizing action on zinc may be introduced into chamber 4, for example, through a pipe or conduit 12.

Our process may also be carried out in any other suitable form of apparatus providing for the essential steps in the operation as above described, for example, in an. apparatus such as shown in Fig. 3, the zinc volatilizing retort 1 in that case discharging into a chamber or flue 4 leading to a filter apparatus such as bags 15 which are provided with suitable'means for removing the collecting material therefrom in the usual manner, such material being withdrawn through a gate means 6 and the gases being withdrawn from the bags through a conduit. 16 by pump or blower 7 and forced back through a conduit 9 into proximity to the outlet 3 of retort 1. In this case We have shown regulatable inlet means or valve 12 for admitting air or other oxidizing gas or vapor to the chamber 4 and the regulatable outlet means or valve 18 for discharging gases from the circulating system in such manner as to maintain the required oxidizing property of the gases into contact with which the zinc vapor is introduced. Oxidizing gases may be introduced at valve 12 continuously or intermittently as may be required, or valves 12 and 18 may be closed and a bag 10 of suitable permeable material may be attached to an opening 11 communicating with chamber 4. The wall of chamber 4 may be provided with an opening normally closed by plug -13 to serve as a side opening and for passage of a tool for cleaning the interior of the casing.

Vhat we claim is:

1. The process for producing metal dust orpowder which consists in producing the vapor of the metal by action of heat on material containing such metal, bringing sucn vapor into contact with a gaseous medium which is at a sufficiently low temperature to cause condensation of the zinc vapor, such gaseous medium beingcapable of producing suflicient oxidation of the metal to insure condensation into finely divided solid particles, removing from the gaseous medium the solid metal particles suspended therein, cooling the gaseous medium and returning it to contact with fresh portions of metal vapor and maintaining a definite and regulated supply of oxidizing agent to the gaseous medium to'maintain the oxidizing. property thereof;

2. The process which consists in subjecting material containing zinc to heat to produce zinc vapor, introducing such vapor into 7 a chamber, introducing into said chamber a relatively cool gaseous medium in such manner that the said medium is brought into contact with the zinc vapor and causes a condensation thereof, removing from the gases, the solid zinc particles produced therer withdrawn and in relatively cool condition to contact with fresh portions of zinc vapor introduced intothe chamber and admittmg to said chamber a definite regulated amount of oxidizin agent to maintain the said gaseous medlum in the chamber in oxidizing condition.

3. A process for production of metal dust or vapor comprising vaporizing metal, introducing the vapor into a gaseous medium containing a limited re ulated supply of oxygen and at a sufiicienfiy low temperature to cause condensation of the vapor, subjecting such gaseous medium to cooling action, circulating such gaseous medlum from a cooler portion thereof to avportion thereof adjacent to the point of introduction of the metallic vapor to effect cooling and condensation of the metallic vapor. 4. A process for production of metal-dust or powder comprising vaporizing the metal and supplying to the vapor a limited amount of gaseous medium containin a limited amount of an oxidizin agent, circulating said gaseous medium gI'OIIl cooler portions thereof to portions adjacent to the point of contact with the metallic vapor so as to condense the vapor by contact with such cooler gaseous medium and collecting the condensed material.

5, A process for production-of zinc dust or powder comprising vaporizing the zinc, introducing the zinc vapor into a body :of gaseous medium moving in a circulatory path, said gaseous medium containing a controlled amount of oxidizing agent and being cooled in a portion of its path in such man ner as to effect condensation of the zinc vapor when introduced thereinto and con-. trolling the supply of oxidizing agentto said 

